In the integrated circuit industry, there is a continuing effort to increase device speed and increase device densities. In addition, manufacturers continue to search for technologies that can be used to implement optical functions at low cost.
Prior U.S. patent application Ser. No. 10/146,351, filed May 15, 2002, Ser. No. 09/991,542, filed Nov. 10, 2001, and Ser. No. 09/859,693, filed May 17, 2001, each of which is owned by the assignee of the present application and herein incorporated by reference, describe various optical components that can be formed at low cost on semiconductor wafers using standard CMOS processing techniques. In these prior applications, an electrode was used to project a region of altered propagation constant into a semiconductor waveguide in order to achieve a given optical function. The present application describes still further optical systems that can be formed on semiconductor wafers.